This application is based on European Patent Application No. 00202088.1 filed on Jun. 16, 2000, the content of which is incorporated hereinto by reference.
The present invention relates to a water-soluble complex of an extract of Ginkgo biloba, to a process for the preparation thereof and to a composition comprising the same.
More particularly, the present invention relates to a water-soluble complex of an extract of Ginkgo biloba with N-methylglucamine.
It is known that the leaves of Ginkgo biloba contain a host of heterogeneous substances formed of both liposoluble and water-soluble compounds.
Extracts of Ginkgo biloba have been studied for years both from a chemical point of view and from a pharmacological and clinical point of view since they comprise compounds endowed with cerebral and peripheral vasomotor activity.
In approximate terms, the dry extracts used in pharmaceuticals have the following composition:
about 24% w/w of heterosides (expressed as flavone glycosides, consisting mainly of quercetin-3-O-(6xe2x80x2xe2x80x3-trans-p-cumaroyl-2xe2x80x3-glucosyl)rhamnoside and kaempferol and isorhamnetin-3-O-(6xe2x80x2xe2x80x3-trans-p-cumaroyl-2xe2x80x3-glucosyl)rhamnoside);
about 6% w/w of bilobalide and ginkgolides J, A, B and C;
about 3-4% w/w of proanthocyanidins (consisting of mixtures of anthocyanidins and delphinidin dimers and polymers);
the balance consisting of not yet clearly identified inert plant matter.
However, the abovementioned extracts are not soluble in water.
To overcome this drawback, patent application WO 00/01397 discloses a water-soluble dry extract obtained from an hydroalcoholic extract of Ginkgo biloba leaves by means of targeted ultrafiltration.
Patent application FR-A-2 755 015 discloses an extract of flavonoids from Ginkgo biloba leaves, with a low content of other components, which has anti-elastase and anti-inflammatory activity on human gums. The said document also describes a pharmaceutical composition containing the abovementioned extract for the topical treatment of the abovementioned complaints. The pharmaceutical compositions can also be in liquid form. However, the document never mentions aqueous solutions since the abovementioned extract is not water-soluble.
Thus, there is still a great need for an extract of Ginkgo biloba leaves which is particularly rich in flavonoids and which has a low content of other components, and which is also water-soluble.
In the present description and in the claims, the term xe2x80x9cwater-solublexe2x80x9d means a solubility in water of at least 1% (w/v).
It has now been found, surprisingly, that this aim can be achieved by forming a complex of an extract of Ginkgo biloba with N-methylglucamine. Indeed, it was entirely unpredictable that N-methylglucamine would interact with many of the components of the abovementioned extract which lack an acid function.
It is therefore a first object of the present invention to provide a water-soluble complex of N-methylglucamine with an extract of Ginkgo biloba leaves.
Furthermore, it is a second object of the present invention to provide a process for preparing a water-soluble complex of an extract of Ginkgo biloba leaves with N-methylglucamine, the said process comprising the steps of:
a) adding N-methylglucamine to an alcoholic solution of the said extract,
b) filtering the solid product obtained from step a), and
c) removing the solvent.
The composition of the extract of Ginkgo biloba leaves reacted with N-methylglucamine is preferably as follows:
flavone glycosides: 22-45% (w/w),
ginkgolides 0.1-12% (w/w),
bilobalide: 0.01-5% (w/w),
proanthocyanidins: 3-8% (w/w).
The amount of extract reacted on a dry-weight basis is preferably of about 1.5-3.0 times and even more preferably to twice the weight of the N-methylglucamine.
The said alcoholic solution is typically a solution of a saturated aliphatic alcohol having of from 1 to 4 carbon atoms and having a linear or branched chain, such as, for example, methanol, ethanol or isobutanol.
Preferably, step a) is carried out at a temperature of between 0xc2x0C and the boiling point of the reaction mixture. Even more preferably, this temperature is between 20 and 70xc2x0 C.
Step c) is typically carried out by evaporating off the solvent under reduced pressure.
The composition of the thus obtained water-soluble complex is advantageously as follows:
flavone glycosides: 15-30% (w/w),
ginkgolides: 0.1-7% (w/w),
bilobalide: 0-2% (w/w),
proanthocyanidins: 1-2% (w/w)
N-methylglucamine: 32-34% (w/w),
water-soluble inert plant matter: 25-51.9% (w/w).
Finally, it is a third object of the present invention to provide a composition comprising a water-soluble complex of N-methylglucamine with an extract of Ginkgo biloba leaves, characterized in that the said complex is rich in flavonoids and has a low content of other components.
The said complex typically has a water solubility of between 1 and 30% (w/v), and even more typically the said solubility is of from 3 to 10% (w/v).